Field of the Invention
The present invention relates to a method for obtaining policy information for traffic offload.
Related Art
In 3GPP for regulating the technical standards of the 3rd mobile communication system, from the end of the year 2004, there have been started researches on Long Term Evolution/System Architecture Evolution (LTE/SAE) technology as part of an effort to optimize and improve the performance of 3GPP technologies in order to handle several forums and new technologies related to a 4th mobile communication.
SAE that has been in progress based on 3GPP SA WG2 is research regarding a network technology for the purposes of determining the configuration of a network and supporting mobility between heterogeneous networks along with the LTE task of a 3GPP TSG RAN, and SAE is one of the recent important standardization issues of 3GPP. In SAE, a task has been in progress for the purposes of an optimized packet-based system with minimized transmission delay through a further improved data transfer capability as a task for developing a 3GPP system into a system that supports various radio access technologies based on an IP.
An SAE higher level reference model defined in 3GPP SA WG2 includes non-roaming cases and roaming cases including various scenarios. For the detailed contents of the SAE higher level reference model, reference may be made to 3GPP standard document TS 23.401 and TS 23.402. A simple reconfiguration of the SAE higher level reference model is illustrated in a network configuration of FIG. 1.
FIG. 1 illustrates the configuration of an evolved mobile communication network.
One of the greatest characteristics of the network configuration of FIG. 1 is that the network configuration is based on the eNodeB of an evolved UTRAN and the 2 tier model of a gateway of a core network. An eNodeB 20 includes the functions of the NodeB and RNC of an existing UMTS system although they are not precisely matched, and the gateway may be considered to have the SGSN/GGSN functions of the existing system.
Another important characteristic is that a control plane and a user plane between an access network and a core network are exchanged through different interfaces. In an existing UMTS system, one Iu interface was present between an RNC and an SGSN. In contrast, in this network configuration, a Mobility Management Entity (MME) 51 responsible for the processing of control signals is configured to be separated from a gateway (GW), and thus two interfaces S1-MME and S1-U are individually used. The GW includes a Serving-GW (hereinafter referred to as an ‘S-GW’) 52 and a Packet Data Network GW (hereinafter referred to as a ‘PDN-GW’ or a ‘P-GW’) 53.
FIG. 2 is a diagram illustrating a relationship between an (e)NodeB and a Home (e)NodeB.
In the 3rd or 4th mobile communication system, attempts to increase a cell capacity continue to be made in order to support high-capacity services and bidirectional services, such as multimedia content and streaming.
That is, as various high-capacity transmission technologies are required in line with the development of communication and the spread of multimedia technologies, there is a method of allocating more frequency resources as a method of increasing a radio capacity, but to allocate more frequency resources to a plurality of users using limited frequency resources is limited.
In order to increase the cell capacity, there has been an approach for using a higher frequency band and reducing cell coverage. If a cell having small cell coverage, such as a pico cell, is used, there is an advantage in that more information may be transferred because a band higher than a frequency used in an existing cellular systems may be used. However, there is a disadvantage in that expenses are increased because more base stations must be installed in the same area.
Approaches for increasing the cell capacity using a small cell as described above include a femto base station, such as a Home (e)NodeB 30 that has recently been proposed.
An (e)NodeB 20 illustrated in FIG. 2 may correspond to a macro base station, and the Home (e)NodeB 30 illustrated in FIG. 2 may become a femto base station. This specification is described based on the terms of 3GPP, and an (e)NodeB is used to denote a NodeB or an eNodeB. Furthermore, a Home (e)NodeB is used to denote both a Home NodeB and a Home eNodeB.
Interfaces indicated by dotted lines are for transmitting control signals between the (e)NodeB 20 and the Home (e)NodeB 30, and the MME 510. Furthermore, interfaces indicated by solid lines are for transmitting the data of a user plane.
FIG. 3 illustrates conventional problems.
As illustrated in FIG. 3, if traffic is overloaded or congested in the interface between the (e)NodeB 20 and an S-GW 52 or traffic is overloaded or congested in the interface between the Home (e)NodeB 30 and the S-GW 52, downlink data toward UE 10 or upload data from the UE 10 is not correctly transmitted, thus resulting in a failure.
Alternatively, if the interface between the S-GW 52 and a PDN-GW 53 or the interface between the PDN-GW 53 and an Internet Protocol (IP) service network of a mobile communication service provider is overloaded or congested, downlink data toward the UE 10 or upload data from the UE 10 is not correctly transmitted, thus resulting in a failure.
Furthermore, there is a problem in that the service of the UE is dropped if another cell has been overloaded when the UE performs a handover from a current cell from which the UE is supplied with the service to another cell.
In order to solve the problems, mobile communication service providers have changed the S-GW 52 and the PDN-GW 53 into an S-GW and PDN-GW of a higher capacity or have increased new equipment. However, there is a disadvantage in that high expenses are required. Furthermore, there is a disadvantage in that the S-GW and the PDN-GW of a higher capacity or the new equipment is shortly overloaded because the amount of transmitted and received data is increased by geometrical progression.
Meanwhile, there have been proposed various schemes for optimizing the S-GW 52 and the PDN-GW 53 without increasing a mobile communication network as described above. For example, there has been proposed a technology in which in a macro access network, specific IP traffic (e.g., Internet service) of UE is transmitted through a selected optimum path, and in a femto access network (e.g., a Home (e)NB), the specific IP traffic is offloaded to a path through the nodes of a public network, that is, a wired network, not a mobile communication network without transmitting and receiving the specific IP traffic to and from a path through a mobile communication network.
FIG. 4 illustrates a concept of Selected IP Traffic Offload (SIPTO).
FIG. 4 is an exemplary diagram illustrating a mobile communication system, such as an Evolved Packet System (EPS). The EPS system includes an (e)NodeB 20, an MME 51, an S-GW 52, and a P-GW 53. Furthermore, a Home (e)NodeB 30 is illustrated.
As illustrated, in the Selected IP Traffic Offload (SIPTO) technology, specific IP traffic (e.g., Internet service) of UE 10 is offloaded to the nodes of a wired network 70 without passing through nodes within the IP service network 60 of a mobile communication service provider.
For example, if UE 10 receives a grant to access the (e)NodeB 20 or the Home (e)NodeB 30, the UE 10 may generate a session via the wired network 70, such as a public communication network, through the (e)NodeB 20 or the Home (e)NodeB 30 and perform IP network service through the session. In this case, a service provider policy and subscription information may be taken into consideration.
In order for the session to be generated as described above, a gateway installed at a location close to the (e)NodeB 20 or the Home (e)NodeB 30 may be used as a gateway, that is, a local gateway responsible for some of the functions of a GGSN in the case of an UMTS or a local gateway responsible for some of the functions of a PDN Gateway (P-GW) in the case of an EPS.
Such a local gateway is called a local GGSN or a local P-GW. The function of the local GGSN or local P-GW is similar to that of a GGSN or P-GW.
As described above, the SIPTO technology has proposed a concept in which the data of UE is offloaded to a wired network, such as a public communication network, through the (e)NodeB 20 or the Home (e)NodeB 30.